The present invention relates generally to detection and monitoring of electrical signals generated by the brain and, more particularly, to equipment for electrically connecting human subjects to brain wave detection instrumentation.
Electrical energy produced by the brain is detectable by placement of electrodes in conductive low impedance contact with the scalp. Positive connection of each electrode is critical to obtaining valid EEG signals. Hair and dirt on the scalp are the primary impediments to establishing a good electrical contact with an electrode to the scalp. Conventional scalp electrode attachment is very tedious and labor intensive, requiring either hair removal or displacement, scalp cleaning, and in some cases application of a conductive agent such as gel or solution between the electrode and the scalp. Typical clinical EEG analysis requires at least nineteen electrodes to be attached to the scalp, and advanced analysis may require 100 or more electrodes. This is very time consuming and largely impractical for many types of EEG usage such as biofeedback training.
Different systems have been devised to provide quick connection electrode arrays for the scalp. Most of these involve the use of a specialized cap or strapped-on headgear in which electrodes are mounted. The straps support electrode mounting structures at multiple sites. The electrodes are mounted to protrude from the strap mounts in contact with the scalp. Although these types of devices position multiple electrodes next to the head or hair, they do not necessarily establish positive conductive contact of each electrode with the scalp. The contact of each electrode must still be separately established and confirmed throughout the monitoring process.
The present invention overcomes these and other deficiencies of the prior art, by providing a simple EEG electrode assembly and method which establishes positive conductive contact with the scalp. The invention provides a simple, clean, paste-free and gel-free electrode system for use in EEG, EMG, EKG and related body potential work. The electrode assemblies can be used to establish electrical contact and record biopotentials from the head, face and other body areas. The electrode assemblies are especially advantageous in applications where it is difficult to get a food electrical connection through hair, and where the use of conductive gels or pastes is to be avoided.
In accordance with one general aspect of the invention, there is provided an EEG electrode assembly having an electrode connected to an electrical lead, a fibrous, absorptive and conductive electrode wrapping substantially encompassing the electrode, an electrode holder having an opening for receiving a wrapped electrode, the electrode holder being configured for engagement with a fixture supported by a strap for holding the electrode assembly in contact with a scalp. In one particular embodiment, the electrode holder is a generally cylindrical plug having an internal cylindrical opening for receiving a wrapped electrode, and an engagement structure such as threads on an exterior of the electrode holder for engagement with a corresponding structure in a retaining ring fixture supported by a strap for attachment to a head, in order to place the electrode assembly in positive conductive contact with the scalp. In another aspect of the invention, there are provided multiple electrode holder support structures in different types of head gear such as caps or hats which position the electrode assemblies engaged in the support structures in positive conductive contact with the scalp.
In a particular embodiment of the invention, there is provided an adjustable plastic electrode holder configured to contain an electrode wrapped in a piece of felt, with an electric lead wire extending from the electrode and the felt. The felt is wrapped about the electrode in a rolled manner, and the generally cylindrical felt/electrode assembly fits within a cylindrical cavity in the electrode holder. Male threads are formed on an exterior of the electrode holder, and engaged with female threads in a retaining ring supported by a strap or band or other support structure such as a cap.
In use, the electrode assemblies provide a clean, wet and physically and electrically secure connection to skin by absorption of a conductive saline solution by felt wrapped around the electrode. The absorptive fibrous or fabric electrode wrapping is saturated with a conductive solution to achieve a good electrical connection. Moisture flows from the wrapping to the underlying hair or skin to establish a current path.
These and other aspects of the invention are herein described in detail with reference to the accompanying Figures.